Method of applying heat-sealable labels



Aug. 3, 1948. R. A. FARRr-:LL ET Al. 2,446,434

METHOD OF APPLYING HEAT-SEALABLE LABELS Filed sept. so, 1944 2sheets-sheet 1 J,H/@mz UTS @5c/" Wfegg. Qd Magg/Zal. @new Patented Aug.3, 1948 2,446,414 METHOD oF APPLYING HEAT-SEALABLE LABELS Robert A.Farrell and Charley L. Wagner, Me-

nasha, Wis.,

assignors to tion, Rothschild, Wis.,

consin Marathon Corporaa corporation oi Wis- Application September 30,1944, Serial No. 556,620

Claims. (21S-62) This invention relates to heat-sealable labels which donot have any, exposed coating material on their outer surfaces. Morespeciiically, this invention relates to heat-scalable labels having anadhesive composition provided internally of the label which is notnormally exposed, but which is activated Aand brought to thev surfacethereof to provide an adhesive nlm when it is desired to amx the labelto any desired surface by application of heat and pressure thereto.

Further details and Iadvantages of the invention will be apparent fromthe following speciflcation and drawings wherein:

Figure 1 is a perspective view of `a rectangular heat-sealable labelpartly broken away to show the components thereof,

Figure 2 is an enlarged sectional view taken on lines 2 2 of Figure 1,

Figure.3 is an enlarged sectional view of the label afxed to a base byapplication of heat and pressure to the label, i

Figure 4 is a perspective view of a package Wrapped in Cellophane towhich a label is amxed,

Figure 5 is a perspective view of a sealing label having indicia printedthereon, and

Figure 6 is a perspective view of a roll of the label shown in Figure 5in continuous strip form.

Heat-scalable labels have been provided previously with a surf-acecoating of suitable compositions which are activated or softened byaction of heat when the label is to be sealed to a suitable surface. Inthe label printing and die cutting operation the sheet is repeatedlysubjected to drastic mechanical pressures. Any exposed coatings producedon such equipment tend to separate and accumulate on the dies andcontacting machine parts, progressively build up accumulations whichwould interfere with the operation the equipment. By use of our sheetmaterials t ese diificulties are entirely eliminated as no coating isexposed in our sheet. The stock sheet materials from which we make ourlabels is readily convertible into labels by means of ordinary labelmaking equipment. Furthermore labels having exposed coatings 4aredifficult to handle prior to use due to pressure-sensitive properties ofsome thermoplastic compositions. When such labels are stacked or rolledup the outer coating composition has a tendency to cause blocking orsticking together of the contacting labels. Furthermore, such priorexternal coatings cause difilculty when the labels are handled bymachinery as the coating may adhere to machine parts or scrape on andaccumulate on moving parts and thus prevent efcient operation. There arealso many sticky and soft types of heat-scalable compositions that couldnot be possibly used as exposed external coatings that can now be usedin our heat-scalable labels made in accordance with our invention as thesealing composition of our label is not exposed normally and will notcause blacking or cause adhesion of any contacting materials Thesedisadvantages and difculties have been effectively overcome by ourinvention as we produce an eicient heat-sealable label made ofsuperposed plies of sheet materials without having any external orexposed coating thereon of any kind. According to our invention, ourcomposite labels indicated generally by numeral lo in the drawings aremade from a stock sheet material, indicated by numeral 3 in Figures 1and 2, formed of a relatively impermeable base sheet, provided' with asmooth, continuous, uniform thermoplastic coating film 2 thereon andhaving a. normally non-removable relatively porous cover sheet I adheredto and covering the adhesive film. The cover sheet l is relativelyporous and permeable as compared with the base sheet 3 in regard to theadhesive lm 2 when in softened or molten condition, so that when thelabel is subjected to heat and pressure, the adhesive film 2 willmigrate, pass or strike through the relatively porous cover sheet toprovide a sealing adhesive film 4 as indicated in Figure 3 on thesurface of the porous sheet in sumcient amount to form a strong seal toa supporting surface i2 to which the label is applied.

In practical production of the stock material from which our compositelabels are made We apply the homogeneous thermoplastic heat-sealingadhesive composition 2 as a smooth continuous exible coating of suitableuniform thickness and of a predetermined basis weight on the base sheetby any suitable means and apply the cover sheet to the adhesive layerunder suitable controlled conditions as to prevent penetration of theadhesive therethrough and formation of a surface film on the exposedface of the cover sheet. We may apply our molten adhesive compositionfor example between the base sheet and cover sheet by means of suitablerotating rolls adjusted so as to provide a controlled and predeterminedthickness of nhn between the sheets. The combined sheets may be chilledto control the degree of penetration of the adhesive therethrough. Theviscosity and physical characteristics of theadhesive composition mayalso be suitably controlled to prevent migration of the compositionthrough the cover sheet when the sheets are combined with the adhesive.Instead of applying the adhesive as a continuous film we may apply thecomposition only in certain predetermined areas and of any suitablecontour. The composition, for example, may be applied in the form ofbands or stripes at the margins or other portions between the sheets sothat the sheets are heat-scalable only in such areas. The adhesivecomposition may also be applied by means of knurled or speciallycontoured rollers so as to apply the adhesive in suitably spaced areasor in the form of discrete particles or spots instead of in a continuousfilm form. In such application a sufficient quantity of the adhesive isapplied so that it will migrate through the porous sheet to form a sealor bond.

Any suitable relatively impermeable base sheet material 3 is selecteddepending upon the particular usage of the final product, such as paper,paper board, regenerated cellulose, glassine, parchment paper, rubberhydrochloride, cellulose acetate, ethyl cellulose, vinyl resins, anysuitable synthetic resin foils, metal foils and the like.l The basesheet material may be treated so as to impart any desired additionalcharacteristics thereto such as greater imperviousness to the adhesiveused, wet-strength, greaseproofness and iiexibilityl In the case ofpaper, it may be suitably coated and supercalendered for printingpurposes.

The cover sheet I is selected so as to be relatively porous as comparedwith the relatively impermeable base sheet, 3, and of such structure asto permit migration of the molten or softened adhesive coating layer 2to the surface `of the porous sheet, through the material of the sheetitself or through any interstices, pores, channels, openings orperforations present in the sheet l. In other words, the cover sheet Iis selected so as to have suitable physical or structuralcharacteristics so as to permit the molten or softened adhesive layer 2to migrate or pass outwardly Ato the exposed surface of the poroussheet. Depending upon the type of porous sheet selected, the moltenadhesive will migrate either through the substance of which' the sheetmay be made or through any interstices, pores, channels, slits oropenings existing in the sheet. Light-weight paper tissue, for example,has a porous structure formed by interlacing of cellulosic fibers whichpermits the molten or softened adhesive to pass through the sheetreadily.

We may use any suitable type of porous, woven or reticulated sheets,such as woven and knitted fabrics, netting and the like. We may also usecomparatively dense or impervious sheets, such as parchment paper,glassine, regenerated cellulose, and even metal foils, by providingslits, holes, or openings of suitable dimensions and suitablydistributed throughout such sheet materials or in selected andpredetermined areas so as to permit the molten or softened adhesivelayer 2 to pass through such openings. Instead of using a prefabricatedporous cover sheet we may apply pulp, cotton, wool and similar fibers,to the molten thermoplastic adhesive film 2 immediately after it hasbeenapplied to the base sheet and before it has congealed to form in situthe equivalent of a separately applied cover sheet. The expressionporous sheet or cover sheet" is intended to include any of thepreviously described sheets which permit the softened or molten adhesivelayer 2 to migrate to the surface thereof in sumcient amount to providean adhesive sealing ilm on the outer surface of the porous sheet. Weprefer to use a porous sheet made of lightweight paper tissue relativelylighter in weight than the base sheet, for example, less than 20 lbs.(basis weight 480 sheets 24 x 36 in.) paper sulphite tissue. Such tissuesheet is comparatively porous with respect to the base sheet so as topermit the adhesive layer to migrate differentially in greater amount byweight per unit weight of sheet through the porous sheet rather than therelatively impermeable base sheet so as to generate an' adhesive film onthe outer surface of the relatively porous cover sheet. The porous papercover sheet may be treated if desired with ureaformaldehyde resins, ormelamine resins, in small amounts. say 1 to 5% by weight, to increaseits wet-strength withoutrhowever affecting its porosity and otheroriginal physical characteristics. Both the base sheet and porous papersheethmay be wax-sized or dry-waxed to increase their` waterproofness,moldproofness, machine workability, etc.

In any particular combination of relatively impermeable base sheet andrelatively porous cover sheet the adhesive layer is of such characterthat upon application of heat and pressure to a label made of suchcombined sheet the intermediate layer upon melting or softening will bedriven or migrate differentially through the cover sheet and penetrateto the surface thereof, rather than tend to migrate through the basesheet which resists the migration of the adhesive therethrough as it, isrelatively more impervious and/or dense than the porous sheet. Theadhesive, in other words, will take the path of least resistance andwill penetrate through the relatively porous cover sheet and onlypartially, if at all, through th'e relatively denser base sheet togenerate an adhesive sealing iihn on the surface of theporous sheet.

The cover sheet i may be treated so as to permit migration of theadhesive only at certain prede termined areas. This may be accomplished,for example, by lacquering a porous paper sulphite tissue sheet incertain predetermined areas so th'at the adhesive will not migratethrough the sheet at such treated areas. A dense type of sheet may alsobe provided with suitable openings, slits or pinholes at certainpredetermined areas through which the adhesive may migrate, but notelsewhere.

We nd it advantageous to provide an adhesive nlm of a basis weight of atleast about 11/2 to 2 times or preferably more than the basis weight ofthe porous cover sheet when using, for example, a paper base sheet of 17lb. sulphite and 9 lb. porous sulphite paper sheet (basis weight 480sheets 24 x 36 in.) When such amount of intermediate nim is providedthere will be suicient adhesive composition to bond the sh'eetstogether, and also upon application of heat and pressure, the adhesivecomposition will penetrate and saturate the cover sheet to such extentas to migrate to the surface to provide a suitable bonding film at theouter surface thereof.

Suitable thermoplastic intermediate adhesive coatings which we may useare made of selected or blended microcrystalline waxes; microcrystallinewaxes having one or more added viscosityincreasing ingredients such asvarious elastomers, resins, gums, rubber, synthetic rubber, isobutyleneand butylene polymers, metallic soaps such as aluminum soaps of thehigher fatty acids as aluminum stearate, oleate or palmitate in amountsfrom 1 to 30% by weight; paraiiln wax containing any of the previouslymentioned ingredients added thereto and in about the same amounts;cellulose derivative compositions; synthetic resins, such asphenol-formaldehyde resins, urea-formaldehyde resins, vinyl resins;asphalts; natural gums; protein-containing composition such as zein; andcasein. These compositions are utilized for combining the base sheet andthe cover sheet in any known manner, as previously explained, so as tocontrol selectively the degree of penetration of the composition intothe base and relatively porous sheet. When using thermoplastic hot-meltcompositions having wax as the base ingredient, we may chill thecombined sheets at the point of combining so as to control penetrationor migration vof lthe composition through both combined sheets. Theingredients of the composition used may be suitably selected andcompounded so as to have a suitable predetermined viscosity so as to benonpenetrating with respect to the sheets to be combined. The use ofviscosity-increasing ingredients serves (1) to bring up the viscosity toa point where a greater weight of adhesive can be applied successfullywith the present types of available coating equipment, (2) to make theadhesive of such viscosity that it will penetrate less into the basesheet using, for example, open type of sheets such as board or heavyweight sulphite paper, and yet permit of suilicient penetration throughthe cover sheet to eilect the seal when heat and pressure are applied,(3) to bring up the adhesiveness of certain hot melt materials such asparamn wax, in order to make them usable for the purpose of thisinvention. The conditions under which the sheets are combined, such asspeed of uniting, temperature of application of the adhesive, chillingof the combined sheets also can be controlled in any known m-anner toprevent penetration. In this way vwe obtain a stock sheet from which ourheat-sealable labels are made which has a continuous iiexible uniformlayer of the intermediate sealing composition Without any of thecomposition being present on the outer exposed surfaces of the sheet. Wemay retain the original unimpaired physical surface characteristics ofthe sheet materials used so that they can be printed with any suitableindicia Il for labels and the like, as illustrated in Figure 5, withoutdisturbing the intermediate layer which is activated and provides asealing means only upon application of heat and pressure to the label.

The following are typical specific examples of the stock sheet materiafrom which our heatsealable labels are made, he numerals preceding eachcomponent being the same as in the drawings, weights being given perream (480--24 x 36) COMPONENT Example 1 Pounds weight per ream Example3 1. Porous sulphite tissue paper 9.0 2. 3% aluminum stearate, 5% estergum, and 92% mlcrocrystalline wax M. P. 145 F.,

1. Porous dry waxed sulphite tissue paper 11.0 2. 3% aluminum stcarate,5% ester gum, and

92% microcrystalline wax M. P. 145 F.,

by Wt 25.0 3. Regenerated cellulose l 20.0

Total -56.0 E :rample 5 i l. Porous sulphite tissue paper 9.()` 2. 3%aluminum stearate, 5% ester gum, and 92% microcrystalline Wax M. P. 145F., by Wt 25.0 3. Highly plasticized glassine 30.0

Total 64.0

Example 6 1. Porous sulphite tissue paper 9.0 2. 97% by wt.microcrystalline Wax M. P. 14S-7 F. and 3% by wt. aluminum stearato 19.03. Highly hydrated greaseproof sulphite g paper 17.0

Total 45.0

O ur labels can be formed of any suitable predetermined contour eitheras individual labels as illustrated in Figure 5 or in continuous stripform as illustrated in Figure (i so that they may bey wound up in a rollI8. The strip may be severed along lines i6 by any suitable equipmentprior to heat-sealing the labels to any desired surface.

The exposed face of the dense or relatively impermeable base sheet 3 ofour labels may be printed if desired with any suitable indicia Il asillustrated in Figure 5. Our labels are particularly suitable forapplication by heat and pressure to packages wrapped in Cellophane(regenerated cellulose) as illustrated in Figure 4. The individuallabels are heat-sealed to a sheet of Cellophane or other suitablewrapping material While in flat condition prior to the wrappingoperation so that when a package is wrapped it will have the appearanceas shown, for example, in Figure 4,

the label l0 being aflxed to the exposed surface of the Wrapper 2 I.

Our labels are also adapted for the sealing of ends of wrapped packages.It is also obvious that labels in the form of elongated stripes, bandsand the like may be similarly applied to any part of the body of thepackage. Our labels can be readily heat-sealed to any types of wrappingand sheet materials such as ordinary paper, parchment, glassine,Cellophane, cellulose acetate, Plioiilm (rubber hydrochloride) waxedpapers, lacquered papers, coated papers of all kinds, heat-sealablecoated Cellophane, metal foils, woven and knitted textile fabrics madeof cotton, rayon, nylon, wool, and the like.

The sealing composition we use is heat sensitive upon application ofheat thereto and is adapted to merge or coalesce with ordinary wax or.other types of coatings upon usual wrapping 7. materials used forpackaging purposes. Our labels are adapted particularly to be used uponany type of shellacked or coated papers which are difficult to seal bythe use of glues or similar adhesives which are available on the markettoday. Our labels are adapted also for sealing to cardboard, glass andmetal surfaces, leather and Wood. Our labels can be sealed to almost anydesired surface or object by application of suitable heat and pressurethereto. i

Numerous changes and modiiicationsmay be made in the specificembodiments of our invention utilizing the essential and significantfeatures Vof our invention as fully disclosed herein. It is intended toinclude such modifications Within the scope of the appended claims.

We claim:

l. A method of labeling which comprises providing a label comprising inadhered relation a base sheet material and a relatively porous sheetmaterial adhered to said base sheet by an intermediate thermoplasticadhesive, said adhesive being confined to the inner surface of saidporous sheet and the outer exposed surface of said porous sheet beinglsubstantially unchanged from its original characteristics, positioningsaid labe1 on a supporting surface with said porous sheet in facecontact with said supporting surface, applying heat and pressure to theexposed surface of rather than through said base sheet material and inamount to generate an adhesive sealing film on the outer surface of saidporous sheet to afllx the label to a supporting surface.

2. A method of labeling which comprises providing a label comprising inadhered relation a base sheet material of cellulosic material having arelatively dense structure and a. relatively porous cellulosic sheetmaterial adhered to said base sheet by an intermediate thermoplasticadhesive, said adhesive being confined to the inner surface of saidporouslsheet and the outer exposed surface of said porous sheet beingsubstantially unchanged from its original characteristics, positioningsaid label on a supporting surface with said porous sheet in facecontact with said supporting surface, applying heat and pressure tothe-exposed surface of said base sheet for acti- -vating said adhesiveto migrate differentially through said porous sheet rather than throughsaid base sheet material and in amount to generate an adhesive sealingfilm on the outer surface of said porous sheet' to aiiix the label to asupporting surface.

3. A method of aflixing labels to a supporting surface which comprisesproviding a label comprising in adhered relation a base sheet materialand a relatively porous sheet material adhered to said base sheet by anintermediate thermoplasltic adhesive comprising microcrystalline Wax,

said adhesive being confined to the inner surface of said porous sheetand the outer exposed surface of said porous sheet being substantiallyunchanged from its original characteristics, positioning said label on asupporting surface with said porous sheet in face contact with saidsupporting surface, Aapplying heat and pressure to the exposed surfaceof said base sheet for activating said adhesive to migratedifferentially through said porous sheet rather than through said basesheet material and in amount to generate an adhesive sealing film on theouter surface of said porous sheet to affix the label to a supportingsurface.

4. A method of aflixing labels toa supporting surface which comprisesproviding a. label comprising in adhered relation a base sheet materialand a relatively porous sheet material adhered to said base sheet by anintermediate thermoplastic adhesive comprising microcrystalline wax andaluminum stearate, said adhesive being'confined to the inner surface ofsaid porous sheet and the outer exposed surface of said porous sheetbeing substantially unchanged from its original characteristics,positioning said label on a supporting surface with said porous sheet inface contact with said supporting surface, applying heat and pressure tothe exposed surface of said basesheet for activating said adhesive tomigrate differentially through said porous sheet rather than throughsaid base sheet material and in amount to generate an adhesive sealingfilm on the outer surface of said porous sheet to ailix the label to asupporting surface.

5. A method of aixing labels toa supporting surface which comprisesproviding a label comprising in adhered relation a base sheet materialand a relatively poroussheet material adhered to said base sheet by anintermediate thermoplastic adhesive comprising wax and an elastomer,said adhesive being confined to the inner surface of said porous sheetand the outer exposed surface of said porous sheet being substantiallyunchanged from its original characteristics,I positioning said label ona supporting surface with said porous sheet in face contact with saidsupporting surface, applying heat and pressure to the exposed surface ofsaid base sheet for activating said adhesive to migrate differentiallythrough said porous sheet rather than through said base sheet materialand in amount to generate an adhesive sealing film on the outer surfaceof said porous sheet to aiilx the label to a supporting surface.

ROBERT A, FARRELL. CHARLEY L. WAGNER.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 1,217,819 Peterson Feb. 27, 19171,759,124 MacLaurin May 2.0, 1930 2,054,870 Stelkens Sept. 22, 19362,142,039 Abrams et al Dec. 27, 1938 2,184,139 Cunnington Dec. 19, 1939

